The present invention pertains to a hand-operated jack mechanism suitable for use with a multipurpose jig apparatus of the type including a length of rigid pipe and a plurality of releasable, pipe-gripping, tail stops which are slidably mounted on the pipe.
Multipurpose jigs of this general type use any desired length of standard, steel pipe (alternatively a solid elongate bar or rod may be employed) and the tail stops are formed with bores, fitted to the pipe, so that they may be moved to any selected position along the pipe. Workpiece engaging faces provided on the tail stops may be disposed in inwardly confronting relationship for clamping together opposite sides or edges of a work object. Or the tail stop faces may be arranged in an outwardly opposed relation to exert a spreading force between two objects or between spaced points on the same workpiece.
In one version of the jig, each tail stop is provided with a spring biased, manually releasable dog that is pivotally mounted on the body of the tail stop and is oriented relative to the bore such that a serrated portion of the dog is forced into gripping engagement with the pipe in reaction to a force tending to move the tail stop along the pipe in one given direction. As the applied force in that direction increases, the gripping action of the dog thereby resisting increases resisting any displacement of the tail stop along the pipe. If it is necessary to move the tail stop in that same direction, the dog can be manually released from its gripping position and the stop slid freely along the pipe. A force applied to the tail stop in the opposite direction causes the gripping action of the dog to automatically release and thereby enable the tail stop to be moved freely in such direction without the need to manually disengage the dog.
In this manner, each tail stop may be slid along the pipe until its workpiece engaging face is snugly into contact with the workpiece whereupon the workpiece will be restrained in that position, with the tail stop resisting any counteracting force exerted by the workpiece.
Another version of the multipurpose jig uses tail stops in which the gripping mechanism therefor consists of a stack of annular shaped clutch discs that encircle the pipe and are held in a specially formed portion of the tail stop body. The inside diameter of the stack of discs is oversized with respect to the circumference of the pipe and a spring is associated with the discs, forcing them to a skewed orientation with respect to the pipe so that the discs bind on the outer surface of the pipe, and thereby exert a gripping force that holds the tail stop in place. One or more of the annular discs is formed with a radially projecting portion which may be manually grasped and displaced to force the discs out of their skewed orientation in order to release the gripping action and thereby enable the tail stop to be slid freely along the pipe to the desired position.
In still another version of the jig apparatus, one or more of the tail stops is constructed of two parts forming opposing halves of a split sleeve configuration. The two halves of the split sleeve are formed with interengageable portions which enable each sleeve half to be held against the pipe, on diametrically opposite sides thereof, and then interengaged to assemble the tail stop on the pipe, without requiring it to be slid onto the pipe from an end thereof. In many applications one or both ends of the pipe are inaccessible or obstructed and it is impossible or inconvenient to install the tail stop or stops over an end of the pipe, and in such cases the split sleeve configuration of the tail stops is preferred.
Some tail stops are equipped with screw adjustable clamping mechanisms which can be used to apply a screw-leveraged force (much like a C-clamp) against the workpiece. However, as discussed herein, such screw mechanisms have several drawbacks which limit their usefulness.
While multipurpose jigs of the foregoing type, including the several different versions of tail stop design, have proven utility, nevertheless there are several situations in which currently available jigs and their associated tail stops are incapable of or are unsuitable for being used to perform certain desirable functions, which if available, would complement and thereby enhance the usefulness of such jigs.
It is therefore an object of the invention to provide in combination with such a multipurpose jig apparatus, a hand-operated jack that mounts on the pipe and coacts with one or more of the above types of pipe mounted tail stops in a manner that enables such tail stops to be forcefully displaced along the pipe with a mechanical advantage that is developed by a hand actuated lever.
Another object of the present invention is to provide a hand-operated jack for use with a multipurpose jig apparatus of the above characterized type in order to enhance the versatility of the jig apparatus by enabling it to be used as a lifting jack and/or a hoist.
Another object is to provide such a hand-operated jack for use with a multipurpose jig apparatus of the above-mentioned type which is relatively inexpensive to manufacture, which is durable so as to provide a long trouble-free life, and which is easy to use and reliable so that it can be employed with relative safety and effectiveness by professional craftsmen and hobbyists alike.